Statistical properties of flux closure induced by solar wind dynamic pressure fronts

peer reviewedWe present a statistical study of flux closure intervals induced by solar wind dynamic pressure fronts. We consider that a dynamic pressure front reaches the Earth when a dayside subauroral proton flash is observed in the SI2 channel of the IMAGE-FUV experiment. This pragmatic criterion selects both weak and strong pressure fronts. It is found that the preconditioning of the magnetosphere prior to the pressure pulse arrival mainly governs the magnetospheric response to a weak solar wind dynamic pressure front. This preconditioning includes the amount of open magnetic flux available in the magnetosphere prior to the pressure front arrival and the size of the magnetospheric cavity. However, in the case of a strong pressure pulse, the magnetospheric response is more sensitive to the solar wind properties characterizing the dynamic pressure front. The pressure jump is not the only one important, but also the variation of the solar wind velocity and IMF magnitude. In overall terms, we find that a strong dynamic pressure front is typically characterized by a dynamic pressure increase larger than Ë 2.8 nPa that takes place on timescales of the order of a few minutes

Making a difference for children and families: an appreciative inquiry of health visitor values and why they start and stay in post

The study aimed to develop an understanding of health visitor recruitment and retention by examining what existing staff and new recruits wanted from their job, their professional aspirations and what would encourage them to start and stay in employment. Following a period of steady decline in numbers, the health visitor workforce in England has recently been invested in and expanded to deliver universal child public health. To capitalise on this large investment, managers need an understanding of factors influencing workforce retention and continuing recruitment of health visitors. The study was designed using an interpretive approach and involved students (n = 17) and qualified health visitors (n = 22) from the north and south of England. Appreciative inquiry (AI) exercises were used as methods of data collection during 2012. During AI exercises students and health visitors wrote about ‘a practice experience you have felt excited and motivated by and briefly describe the factors that contributed to this’. Participants were invited to discuss their written accounts of practice with a peer during an audio-recorded sharing session. Participants gave consent for written accounts and transcribed recordings to be used as study data, which was examined using framework analysis. In exploring personal meanings of health visiting, participants spoke about the common aspiration to make a difference to children and families. To achieve this, they expected their job to allow them to: connect with families; work with others; use their knowledge, skills and experience; use professional autonomy. The study offers new insights into health visitors’ aspirations, showing consistency with conceptual explanations of optimal professional practice. Psychological contract theory illustrates connections between professional aspirations and work commitment. Managers can use these findings as part of workforce recruitment and retention strategies and for building on the health visitor commitment to making a difference to children and families

Z-FIRE: ISM properties of the z = 2.095 COSMOS Cluster

We investigate the ISM properties of 13 star-forming galaxies within the z~2 COSMOS cluster. We show that the cluster members have [NII]/Ha and [OIII]/Hb emission-line ratios similar to z~2 field galaxies, yet systematically different emission-line ratios (by ~0.17 dex) from the majority of local star-forming galaxies. We find no statistically significant difference in the [NII]/Ha and [OIII]/Hb line ratios or ISM pressures among the z~2 cluster galaxies and field galaxies at the same redshift. We show that our cluster galaxies have significantly larger ionization parameters (by up to an order of magnitude) than local star-forming galaxies. We hypothesize that these high ionization parameters may be associated with large specific star formation rates (i.e. a large star formation rate per unit stellar mass). If this hypothesis is correct, then this relationship would have important implications for the geometry and/or the mass of stars contained within individual star clusters as a function of redshift.Comment: 11 pages, 5 figures, accepted for publication in Ap

ZFIRE: Using Hα\alpha equivalent widths to investigate the in situ initial mass function at z~2

We use the ZFIRE survey (http://zfire.swinburne.edu.au) to investigate the high mass slope of the initial mass function (IMF) for a mass-complete (log10(M$_*$/M$_\odot$)~9.3) sample of 102 star-forming galaxies at z~2 using their H$\alpha$ equivalent widths (H$\alpha$-EW) and rest-frame optical colours. We compare dust-corrected H$\alpha$-EW distributions with predictions of star-formation histories (SFH) from PEGASE.2 and Starburst99 synthetic stellar population models. We find an excess of high H$\alpha$-EW galaxies that are up to 0.3--0.5 dex above the model-predicted Salpeter IMF locus and the H$\alpha$-EW distribution is much broader (10--500 \AA) than can easily be explained by a simple monotonic SFH with a standard Salpeter-slope IMF. Though this discrepancy is somewhat alleviated when it is assumed that there is no relative attenuation difference between stars and nebular lines, the result is robust against observational biases, and no single IMF (i.e. non-Salpeter slope) can reproduce the data. We show using both spectral stacking and Monte Carlo simulations that starbursts cannot explain the EW distribution. We investigate other physical mechanisms including models with variations in stellar rotation, binary star evolution, metallicity, and the IMF upper-mass cutoff. IMF variations and/or highly rotating extreme metal poor stars (Z~0.1Z$_\odot$) with binary interactions are the most plausible explanations for our data. If the IMF varies, then the highest H$\alpha$-EWs would require very shallow slopes ($\Gamma$>-1.0) with no one slope able to reproduce the data. Thus, the IMF would have to vary stochastically. We conclude that the stellar populations at z~2 show distinct differences from local populations and there is no simple physical model to explain the large variation in H$\alpha$-EWs at z~2.Comment: Accepted to MNRAS. 43 pages, 27 Figures. Survey website: http://zfire.swinburne.edu.au

ZFIRE: A KECK/MOSFIRE Spectroscopic Survey of Galaxies in Rich Environments at z~2

We present an overview and the first data release of ZFIRE, a spectroscopic redshift survey of star-forming galaxies that utilizes the MOSFIRE instrument on Keck-I to study galaxy properties in rich environments at $1.5<z<2.5$. ZFIRE measures accurate spectroscopic redshifts and basic galaxy properties derived from multiple emission lines. The galaxies are selected from a stellar mass limited sample based on deep near infra-red imaging ($\mathrm{K_{AB}<25}$) and precise photometric redshifts from the ZFOURGE and UKIDSS surveys as well as grism redshifts from 3DHST. Between 2013--2015 ZFIRE has observed the COSMOS and UDS legacy fields over 13 nights and has obtained 211 galaxy redshifts over $1.57<z<2.66$ from a combination of nebular emission lines (such as \Halpha, \NII, \Hbeta, \OII, \OIII, \SII) observed at 1--2\micron. Based on our medium-band NIR photometry, we are able to spectrophotometrically flux calibrate our spectra to \around10\% accuracy. ZFIRE reaches $5\sigma$ emission line flux limits of \around$\mathrm{3\times10^{-18}~erg/s/cm^2}$ with a resolving power of $R=3500$ and reaches masses down to \around10$^{9}$\msol. We confirm that the primary input survey, ZFOURGE, has produced photometric redshifts for star-forming galaxies (including highly attenuated ones) accurate to $\Delta z/(1+z\mathrm{_{spec})}=0.015$ with $0.7\%$ outliers. We measure a slight redshift bias of $<0.001$, and we note that the redshift bias tends to be larger at higher masses. We also examine the role of redshift on the derivation of rest-frame colours and stellar population parameters from SED fitting techniques. The ZFIRE survey extends spectroscopically-confirmed $z\sim 2$ samples across a richer range of environments, here we make available the first public release of the data for use by the community.\footnote{\url{http://zfire.swinburne.edu.au}}Comment: Published in ApJ. Data available at http://zfire.swinburne.edu.au, Code for figures at https://github.com/themiyan/zfire_survey, 31 pages, 24 figure

ZFOURGE: Using Composite Spectral Energy Distributions to Characterize Galaxy Populations at 1<z<4

We investigate the properties of galaxies as they shut off star formation over the 4 billion years surrounding peak cosmic star formation. To do this we categorize $\sim7000$ galaxies from $1<z<4$ into $90$ groups based on the shape of their spectral energy distributions (SEDs) and build composite SEDs with $R\sim 50$ resolution. These composite SEDs show a variety of spectral shapes and also show trends in parameters such as color, mass, star formation rate, and emission line equivalent width. Using emission line equivalent widths and strength of the 4000\AA\ break, $D(4000)$, we categorize the composite SEDs into five classes: extreme emission line, star-forming, transitioning, post-starburst, and quiescent galaxies. The transitioning population of galaxies show modest H$\alpha$ emission ($EW_{\rm REST}\sim40$\AA) compared to more typical star-forming composite SEDs at $\log_{10}(M/M_\odot)\sim10.5$ ($EW_{\rm REST}\sim80$\AA). Together with their smaller sizes (3 kpc vs. 4 kpc) and higher S\'ersic indices (2.7 vs. 1.5), this indicates that morphological changes initiate before the cessation of star formation. The transitional group shows a strong increase of over one dex in number density from $z\sim3$ to $z\sim1$, similar to the growth in the quiescent population, while post-starburst galaxies become rarer at $z\lesssim1.5$. We calculate average quenching timescales of 1.6 Gyr at $z\sim1.5$ and 0.9 Gyr at $z\sim2.5$ and conclude that a fast quenching mechanism producing post-starbursts dominated the quenching of galaxies at early times, while a slower process has become more common since $z\sim2$.Comment: Accepted for publication in The Astrophysical Journa

Z-FIRE: ISM PROPERTIES OF THE z=2.095 COSMOS CLUSTER

We investigate the ISM properties of 13 star-forming galaxies within the z~ 2 COSMOS cluster. We show that the cluster members have [N ii]/Halpha and [O iii]/Hbeta emission-line ratios similar to z~ 2 field galaxies, yet systematically different emission-line ratios (by ~0.17 dex) from the majority of local star-forming galaxies. We find no statistically significant difference in the [N ii]/Halpha and [O iii]/Hbeta line ratios or ISM pressures among the z~ 2 cluster galaxies and field galaxies at the same redshift. We show that our cluster galaxies have significantly larger ionization parameters (by up to an order of magnitude) than local star-forming galaxies. We hypothesize that these high ionization parameters may be associated with large specific star formation rates (SFRs; i.e., a large SFR per unit stellar mass). If this hypothesis is correct, then this relationship would have important implications for the geometry and/or the mass of stars contained within individual star clusters as a function of redshift

Love Shouldn't Hurt - E le Sauā le Alofa: Co-designing a theory of change for preventing violence against women in Samoa

Despite the widespread adoption of Theories of Change (ToC) for programme evaluation, the process of collaboratively developing these theories is rarely outlined or critical analysed, limiting broader methodological discussions on co-production. We developed a ToC as part of E le Sauā le Alofa ('Love Shouldn't Hurt') - a participatory peer-research study to prevent violence against women (VAW) in Samoa. The ToC was developed in four phases: (1) semi-structured interviews with village representatives (n = 20); (2) peer-led semi-structured interviews with community members (n = 60), (3) community conversations with 10 villages (n = 217) to discuss causal mechanisms for preventing VAW, and (4) finalising the ToC pathways. Several challenges were identified, including conflicting understandings of VAW as a problem; the linearity of the ToC framework in contrast to intersecting realities of people's lived experiences; the importance of emotional engagements, and theory development as a contradictory and incomplete process. The process also raised opportunities including a deeper exploration of local meaning-making, iterative engagement with local mechanisms of violence prevention, and clear evidence of ownership by communities in developing a uniquely Samoan intervention to prevent VAW. This study highlights a clear need for ToCs to be complemented by indigenous frameworks and methodologies in post-colonial settings such as Samoa

The Influence of Predictability and Controllability on Stress Responses to the Aversive Component of a Virtual Fence

To ensure animal welfare is not compromised, virtual fencing must be predictable and controllable, and this is achieved through associative learning. To assess the influence of predictability and controllability on physiological and behavioral responses to the aversive component of a virtual fence, two methods of training animals were compared. In the first method, positive punishment training involved sheep learning that after an audio stimulus, an electrical stimulus would follow only when they did not respond by stopping or turning at the virtual fence (predictable controllability). In the second method, classical conditioning was used to associate an audio stimulus with an electrical stimulus on all occasions (predictable uncontrollability). Eighty Merino ewes received one of the following treatments: control (no training and no stimuli in testing); positive punishment training with an audio stimulus in testing (PP); classical conditioning training with only an audio stimulus in testing (CC1); and classical conditioning training with an audio stimulus followed by electrical stimulus in testing (CC2). The stimuli were applied manually with an electronic collar. Training occurred on 4 consecutive days with one session per sheep per day. Sheep were then assessed for stress responses to the cues by measuring plasma cortisol, body temperature and behaviors. Predictable controllability (PP) sheep showed no differences in behavioral and physiological responses compared with the control treatment (P P